1. Field of the Invention
The invention relates to imaging devices, and more particularly to solid-state imaging devices with a thinned dimension and methods of fabricating the same.
2. Description of the Related Art
Image devices have been widely used in various image-capturing apparatuses, for example video cameras, digital cameras and the like. Generally, solid-state imaging devices, for example charge-coupled device (CCD) sensors or complementary metal-oxide semiconductor (CMOS) sensors, have photoelectric transducers such as photodiodes for converting light into electric charges. The photodiodes are formed on a semiconductor substrate such as a silicon chip. Signal charges corresponding to photoelectrons generated in the photodiodes are obtained by a CCD-type or a CMOS-type reading circuit.
Solid-state imaging devices are roughly classified into two groups in terms of the direction of light incident on a light receiving unit. One is front-side illuminated (FSI) imaging devices that receive light incident on the front side of a semiconductor substrate on which a wiring layer is formed. The other is back-side illuminated (BSI) imaging devices that receive light incident on the back side of a semiconductor substrate on which no wiring layer is formed.
These FSI and BSI imaging devices usually have a light shielding layer for blocking light between pixels to improve sensitivity and prevent color mixture. Referring to FIG. 1, a cross section of an imaging device 10 is shown. The imaging device 10 includes a semiconductor substrate 11 having photodiodes (not shown) formed therein. A light shielding layer 13 is formed on the semiconductor substrate 11. An insulating layer 15 is formed to cover the light shielding layer 13. In addition, the imaging device 10 includes a color filter layer 17 and a microlens 19 formed over the insulating layer 15.
In the imaging device 10, the light shielding layer 13 and the insulating layer 15 are disposed between the color filter layer 17 and the semiconductor substrate 11. Therefore, a total thickness of the imaging device 10 cannot be reduced. Besides, in BSI imaging devices, an incident light reaches the photodiodes on the back side of the semiconductor substrate 11 without passing a wiring layer on the front side of the semiconductor substrate 11. Therefore, an optical cross-talk issue occurs more easily between adjacent pixels in BSI imaging devices than FSI imaging devices.